RFQ Today
Certifications available: EN 10204 3.1 / 3.2 MTRs, NACE MR0175 compliance, ASTM A193 / A307 / F593, ISO 898 / ISO 3506, Third-Party Inspection, and complete EPC export documentation packages.
Threaded Rod
A world-class technical reference for EPC contractors, structural and piping engineers, procurement heads, TPI inspection agencies, and global project buyers specifying threaded rod in pipe hangers, equipment supports, chemical anchor assemblies, tie rods, tension members, and general structural connections across Oil & Gas, Power Generation, Petrochemical, Infrastructure, Offshore, and Industrial Construction.
Product Types &
Load Characteristics
Threaded rod — also termed all-thread rod (ATR), stud rod, or continuously threaded rod — is a fastener element with a continuous external thread along its full length, supplied in standard bar lengths (typically 1 m, 3 m, or 6 m) or cut-to-length, and used with nuts at both ends to create tension connections, support assemblies, anchor systems, and adjustable structural tie members throughout EPC construction.
1.1 — Technical Definition and Functional Role in EPC
A threaded rod is a straight cylindrical bar of uniform cross-section carrying a continuous helical thread along its entire length to one of the recognised thread standards — metric coarse (ISO 261 / DIN 975), metric fine, UNC, or UNF (ASME B1.1). Unlike a bolt, which has an integral head, threaded rod relies entirely on nuts, couplers, or embedded embedment plates for load transfer at each end and at any intermediate point along its length. This makes it uniquely versatile for adjustable length connections, long-reach tension assemblies, and through-connection configurations that cannot accommodate a bolt head.
In EPC and industrial construction, threaded rod is the primary element in: pipe hanger and support rod assemblies (MSS SP-58, ASME B31.1, B31.3), equipment and vessel saddle support rods, chemical anchor stud assemblies embedded in concrete (ETAG 001 / EN 1992-4), pipe rack bracing tension members, turnbuckle and clevis rod end assemblies, pre-tensioned tie rod systems in steel structures, hold-down rods for seismic-resistant equipment mounting, and high-voltage cable tray longitudinal bracing. The same rod product is supplied in a wide range of material grades and coatings to match the structural, thermal, and corrosion demands of each application.
RR Hydraulic manufactures and supplies threaded rod under all applicable international standards with EN 10204 3.1 / 3.2 material traceability and full project documentation.
1.2 — Threaded Rod Product Type Classification
Fully Threaded Rod (All-Thread) — DIN 975
Continuous thread along the full bar length. Supplied in 1 m and 3 m standard lengths; cut-to-length on order. Per DIN 975 (metric coarse) — the standard product for pipe hanger rod assemblies, chemical anchor systems, and general structural tension connections throughout European and global EPC projects. Property classes 4.8, 5.6, 8.8, 10.9 per ISO 898-1.
Precision Stud Rod — DIN 976
Precision-machined threaded rod with controlled straightness and dimensional tolerance tighter than DIN 975. Per DIN 976-1 (metric) — used in precision structural connections, machine mounting, and applications requiring controlled thread fit and dimensional accuracy. Property classes and material grades per ISO 898-1; thread tolerance 6g (external) per ISO 965.
Partially Threaded Stud / Anchor Bolt
Plain (unthreaded) shank with threaded ends of specified length. Used in anchor bolt applications, where the plain shank provides a smooth bearing zone through a clearance hole in the base plate, and the threaded ends accept nuts above and below. The unthreaded shank section concentrates yield deformation (ductility) in seismic-designed connections. Per ASTM F1554 (anchor bolts) and project-specific specifications.
High-Temperature Alloy Rod — ASTM A193 B7
Chromium-molybdenum alloy steel (4140/4142/4145) threaded rod for high-temperature process equipment, steam systems, and pressure vessel flanged connections. ASTM A193 Grade B7 (full-length continuous thread): yield 725 MPa, UTS 860–1000 MPa depending on diameter. Temperature service to +454°C. Companion to A194 Grade 2H heavy hex nuts. Standard for high-pressure flange bolting and process equipment base plate anchoring.
NACE-Compliant Rod — ASTM A193 B7M
Identical alloy to B7 but controlled hardness — maximum 22 HRC (235 HB) per NACE MR0175 / ISO 15156. Required for all threaded rod in H₂S sour service environments: chemical anchor rods in sour process areas, tie rods on amine plant structures, and hanger rods in sour gas piping systems. Supplied with EN 10204 3.1 hardness test certificate showing individual lot hardness values.
Stainless Steel Rod — ASTM F593 / ISO 3506
Austenitic SS (Grade 304 / 316) or duplex SS threaded rod for marine, coastal, chemical, offshore, and food-grade environments. ASTM F593 (inch UNC/UNF) and ISO 3506 A4-70 / A4-80 (metric) are the governing standards. SS 316 (A4) is mandatory for offshore and marine applications. Duplex 2205 for extreme chloride and sour service. Full passivation per ASTM A967 standard on all SS rod supply.
1.3 — Threaded Rod vs Stud Bolt vs Anchor Bolt: Selection Logic
| Parameter | Threaded Rod (ATR) | Stud Bolt (B16.5) | Anchor Bolt (ASTM F1554) | Engineering Implication |
|---|---|---|---|---|
| Thread coverage | Full length — 100% | Both ends (specific length) | One or both ends threaded | ATR: maximum length flexibility; cut to any length |
| Head | No head — nuts both ends | No head — nuts both ends | Hook, L-bend, or nut at embed end | ATR: fully reversible; no orientation |
| Length adjustment | Yes — field cut to length | Fixed to standard table length | Fixed per design | ATR: preferred for field-adjusted pipe hangers |
| Standard | DIN 975 / ISO 898 / ASTM A307 | ASME B16.5 / ASTM A193 | ASTM F1554 Grade 36/55/105 | Select per applicable project code |
| Primary EPC use | Hangers, anchors, tie rods, supports | Pressure flange bolting | Foundation, base plate anchorage | ATR: most versatile structural rod product |
| Load capacity | Per property class / grade | Per ASTM A193 grade | Per ASTM F1554 grade | Verify grade against design load |
| Nut compatibility | Standard hex nuts (ISO 4032) | Heavy hex nuts (ASME B18.2.2) | Heavy hex or anchor plate | ATR with standard nuts; stud bolt with heavy hex |
1.4 — Load Characteristics and Structural Behaviour
Axial Tension (Primary Load)
The primary structural load mode for threaded rod in hangers, support rods, and tie rod assemblies. Design tensile capacity = A_s × S_y × φ (or ÷ safety factor), where A_s is the thread stress area. For ASME B31.1 / B31.3 pipe hanger design: allowable rod stress = 0.6 × S_y at design temperature. Rod length, diameter, and grade must be selected to limit rod axial stress below the allowable under the worst-case pipe system load condition.
Buckling Under Compression
Threaded rod in compression (struts, push rods, lateral bracing) is susceptible to Euler column buckling. Slenderness ratio λ = L/r where r = d/4 for solid circular section. For λ > 120, Euler buckling governs and rod diameter must be significantly increased. In EPC hanger assemblies, threaded rod is almost always loaded in tension — compressive loading is rare and must be flagged for explicit buckling check by the structural engineer.
Thread Engagement and Nut Turn-Off
The minimum thread engagement length in the nut must exceed the tensile capacity of the rod body — otherwise the nut threads strip before the rod yields. For standard ISO hex nuts: minimum engagement = 0.8×d for property class 8 nuts on Grade 8.8 rod; 1.0×d for Grade 10.9. For chemical anchor applications: embedment depth governs pull-out; the nut engagement is not the limiting factor — substrate bond failure governs.
Thermal Elongation in High-Temperature Systems
Hanger rods connected to hot pipe systems elongate thermally — ΔL = α × L × ΔT, where α = 12×10⁻⁶ /°C for carbon steel; 17×10⁻⁶ /°C for austenitic SS. For a 3 m hanger rod at ΔT = 300°C: ΔL_CS = 10.8 mm; ΔL_SS = 15.3 mm. Variable spring hangers absorb this movement; rigid hanger designs must account for the thermal load and rod elongation in the pipe stress analysis.
Fatigue and Vibration
Threaded rod in vibrating systems (compressor piping, pump discharge lines, reciprocating machinery supports) is susceptible to fatigue cracking at the first engaged thread under the nut — the highest stress concentration location on the rod. Prevention: use rolled threads (compressive residual stress); maintain adequate preload (prevents cyclic unloading); install vibration-absorbing rubber mounts or spring hanger elements; use Nord-Lock or castellated nuts with cotter pins in high-vibration environments.
Corrosion at Nut Interface
The nut-to-rod interface is the most corrosion-vulnerable location on a threaded rod assembly — galvanic cell action, crevice geometry, and bimetallic contact concentrate corrosion attack at this point. In marine and offshore service: rod and nut must be the same material grade (SS 316 rod + SS 316 nut; galvanised rod + galvanised nut). Never install plain carbon steel nuts on SS rods in marine environments — galvanic corrosion accelerates nut attack at the rod thread.
1.5 — Tensile Capacity and Rod Sizing
A_s = Thread stress area (mm²) — per ISO 898-1 or ASME B1.1 table
S_allow = Allowable tensile stress = 0.6 × S_y (ASME B31.1 / MSS SP-58 approach)
S_y = Minimum yield strength of rod material at design temperature (MPa)
Proof load (factory preload verification):
F_proof = A_s × S_p
S_p = proof stress per ISO 898-1 (e.g., Grade 4.6: 225 MPa; 8.8: 640 MPa; 10.9: 940 MPa)
Euler buckling check (compression rods only):
F_cr = π² × E × A / λ² (λ = L_eff / r; r = d/4 for solid rod)
A_s = 245 mm² (M20 × 2.5 stress area per ISO 898-1)
S_y (Grade 4.6) = 240 MPa → S_allow = 0.6 × 240 = 144 MPa
F_allow = 245 × 144 = 35,280 N = 35.3 kN > 15 kN design load ✓
Utilisation ratio = 15.0 / 35.3 = 42% — acceptable; M16 Grade 4.6 could also be verified.
| Rod Size | Stress Area (mm²) | Grade 4.6 (kN) | Grade 4.8 (kN) | Grade 8.8 (kN) | Grade 10.9 (kN) | A193 B7 (kN) | A4-70 SS (kN) |
|---|---|---|---|---|---|---|---|
| M8 | 36.6 | 5.3 | 6.3 | 14.1 | 20.7 | 19.0 | 9.9 |
| M10 | 58.0 | 8.4 | 9.9 | 22.3 | 32.7 | 30.2 | 15.7 |
| M12 | 84.3 | 12.1 | 14.4 | 32.4 | 47.6 | 43.8 | 22.8 |
| M16 | 157.0 | 22.6 | 26.8 | 60.4 | 88.6 | 81.6 | 42.4 |
| M20 | 245.0 | 35.3 | 41.8 | 94.2 | 138.2 | 127.4 | 66.2 |
| M24 | 353.0 | 50.8 | 60.2 | 135.7 | 199.1 | 183.6 | 95.3 |
| M30 | 561.0 | 80.8 | 95.7 | 215.7 | 316.4 | 291.7 | 151.5 |
| M36 | 817.0 | 117.6 | 139.3 | 314.1 | 461.0 | 424.8 | 220.6 |
| M42 | 1121.0 | 161.4 | 191.0 | 430.9 | 632.2 | 582.6 | 302.7 |
| M48 | 1473.0 | 212.1 | 250.9 | 566.3 | 830.7 | 765.5 | 397.7 |
Submit your rod schedule, grade, diameter, length, material, coating, and quantity for a documented RFQ within 24 hours.
Thread Systems &
Standards Compliance
Threaded rod dimensions — outer diameter, thread pitch, minor diameter, stress area, and standard lengths — are governed by DIN 975 / DIN 976 (metric), ISO 261 / ISO 965 (thread form), and ASME B1.1 (UNC/UNF inch). All applicable standards are supported with full material certification at RR Hydraulic.
Submit diameter, thread, grade, length, material, coating, and quantity to sales@rrhydraulics.com for a fully certified offer.
2.1 — Metric Threaded Rod Full Dimensional Table
| Designation | Nominal Dia d (mm) | Pitch p (mm) | Minor Dia d₃ (mm) | Stress Area A_s (mm²) | WAF of Matching Nut (mm) | Standard Lengths (m) | Weight (kg/m) — Steel |
|---|---|---|---|---|---|---|---|
| M6 × 1.0 | 6.0 | 1.00 | 4.77 | 20.1 | 10 | 1, 2, 3 | 0.222 |
| M8 × 1.25 | 8.0 | 1.25 | 6.47 | 36.6 | 13 | 1, 2, 3 | 0.395 |
| M10 × 1.5 | 10.0 | 1.50 | 8.16 | 58.0 | 16 | 1, 2, 3 | 0.617 |
| M12 × 1.75 | 12.0 | 1.75 | 9.85 | 84.3 | 18 | 1, 2, 3 | 0.888 |
| M16 × 2.0 | 16.0 | 2.00 | 13.55 | 157.0 | 24 | 1, 2, 3 | 1.578 |
| M20 × 2.5 | 20.0 | 2.50 | 16.93 | 245.0 | 30 | 1, 2, 3, 6 | 2.467 |
| M24 × 3.0 | 24.0 | 3.00 | 20.32 | 353.0 | 36 | 1, 2, 3, 6 | 3.550 |
| M27 × 3.0 | 27.0 | 3.00 | 23.32 | 459.0 | 41 | 1, 3, 6 | 4.500 |
| M30 × 3.5 | 30.0 | 3.50 | 25.71 | 561.0 | 46 | 1, 3, 6 | 5.550 |
| M36 × 4.0 | 36.0 | 4.00 | 31.09 | 817.0 | 55 | 1, 3, 6 | 7.990 |
| M42 × 4.5 | 42.0 | 4.50 | 36.48 | 1121.0 | 65 | 1, 3, 6 | 10.858 |
| M48 × 5.0 | 48.0 | 5.00 | 41.87 | 1473.0 | 75 | 1, 3, 6 | 14.175 |
| M56 × 5.5 | 56.0 | 5.50 | 49.25 | 2030.0 | 85 | 1, 3, 6 | 19.274 |
| M64 × 6.0 | 64.0 | 6.00 | 56.64 | 2676.0 | 95 | 1, 3, 6 | 25.197 |
2.2 — ASME B1.1 Inch Series Threaded Rod Dimensional Table
| Size | Nominal Dia (in) | TPI (UNC) | Minor Dia (in) | Stress Area (in²) | Stress Area (mm²) | Allowable Load Gr.5 (kN) | Allowable Load B7 (kN) |
|---|---|---|---|---|---|---|---|
| 3/8″ | 0.375 | 16 | 0.2938 | 0.0775 | 50.0 | 12.0 | 26.0 |
| 1/2″ | 0.500 | 13 | 0.3978 | 0.1419 | 91.6 | 22.0 | 47.6 |
| 5/8″ | 0.625 | 11 | 0.5068 | 0.2260 | 145.8 | 35.0 | 75.8 |
| 3/4″ | 0.750 | 10 | 0.6201 | 0.3340 | 215.5 | 51.7 | 112.0 |
| 7/8″ | 0.875 | 9 | 0.7307 | 0.4620 | 298.1 | 71.5 | 155.0 |
| 1″ | 1.000 | 8 | 0.8376 | 0.6060 | 391.0 | 93.8 | 203.4 |
| 1-1/4″ | 1.250 | 7 | 1.0644 | 0.9690 | 625.2 | 149.8 | 325.1 |
| 1-1/2″ | 1.500 | 6 | 1.2835 | 1.4050 | 906.5 | 217.1 | 471.4 |
| 1-3/4″ | 1.750 | 5 | 1.4902 | 1.9000 | 1225.8 | 293.6 | 637.4 |
| 2″ | 2.000 | 4.5 | 1.7113 | 2.5000 | 1613.0 | 386.1 | 838.8 |
2.3 — Applicable Standards and Compliance Framework
DIN 975 / DIN 976
The primary dimensional standards for metric threaded rod in European and global EPC projects. DIN 975: metric coarse fully threaded rod in standard 1 m and 3 m lengths; thread tolerance 6g (external) per ISO 965. DIN 976-1: metric precision stud rods with tighter dimensional tolerance. Available in property classes 4.8, 5.6, 8.8, 10.9, A4-70, and A4-80 per material designation on the purchase order.
ISO 898-1
Mechanical properties of fasteners — bolts, screws, and studs. Property classes 4.6, 4.8, 5.6, 8.8, and 10.9 govern carbon and alloy steel threaded rod mechanical requirements. Defines UTS, proof strength, yield strength, elongation, and hardness for each class. Property class marking on rod end face (when possible) or on packaging. Class 4.8 is the standard for general EPC hanger and support rod; 8.8 for structural tension rods.
ASTM A193 B7 / B7M
High-strength alloy steel bolting for high-temperature and pressure vessel service. B7 (Cr-Mo alloy): UTS 860–1000 MPa (varies with diameter); yield 725 MPa; suitable for −45°C to +454°C. B7M (NACE-compliant): same alloy, controlled hardness ≤ 235 HB / 22 HRC for H₂S sour service. Standard rod material for high-pressure process equipment base plate anchoring and elevated-temperature structural connections in EPC Oil & Gas and power plant projects.
ASTM A307
Standard specification for carbon steel bolts, studs, and threaded rod — Grade A (general structural) and Grade B (anchor bolt and structural purposes). Grade A: UTS 415–550 MPa minimum; used for general light structural connections, pipe hanger rods, non-critical support assemblies. The standard low-cost carbon steel threaded rod for EPC construction site utility and non-critical structural applications. Companion nut: ASTM A563 Grade A heavy hex.
ASTM F593
Stainless steel bolts, hex cap screws, and stud bolts — inch series. Groups 1 (SS 304 / 304L), 2 (SS 316 / 316L), 3 (SS 321 / 347), 4 (SS 22Cr duplex). Condition CW (strain-hardened) provides higher strength than solution-annealed (SH) condition. Used for inch UNC/UNF stainless threaded rod in North American EPC specifications. Companion nut: ASTM F594 stainless hex nuts.
ISO 3506
Mechanical properties of corrosion-resistant stainless steel fasteners. A2-70 / A2-80 (SS 304) and A4-70 / A4-80 (SS 316) for metric stainless threaded rod. A4-70 (SS 316) is the minimum grade for coastal and offshore service; A4-80 for higher-load stainless structural connections. The governing standard for metric SS threaded rod supply in European and international EPC projects requiring corrosion-resistant rod material.
ASTM F1554
Anchor bolts, steel, 36, 55, and 105 ksi yield strength — the governing standard for structural anchor bolts embedded in concrete. Grade 36 (S_y = 248 MPa): weldable, used in non-seismic standard column base plate anchors. Grade 55 (S_y = 380 MPa): medium strength. Grade 105 (S_y = 724 MPa): high-strength, non-weldable, for heavy-load equipment base plate anchoring. Companion standard to chemical anchor design where ASTM F1554 rods are used as the steel element.
MSS SP-58 / ASME B31.1
MSS SP-58: Pipe hangers and supports — materials, design, manufacture, selection, application, and installation. Defines allowable rod stress for carbon steel hanger rod as 0.6 × S_y at temperature. ASME B31.1 Power Piping: hanger rod sizing method for power plant process piping. ASME B31.3 Process Piping: equivalent requirement for EPC process piping. These standards govern the majority of threaded rod sizing in EPC pipe support engineering.
2.4 — Thread Form and Tolerance Reference
| Thread System | Standard | External Thread Class | Internal Thread (Nut) Class | Fit Type | Primary EPC Application |
|---|---|---|---|---|---|
| Metric Coarse | ISO 965 / DIN 975 | 6g (standard) | 6H | Medium clearance | All general hanger, support, anchor rod |
| Metric Coarse (precision) | ISO 965 / DIN 976 | 4g | 5H | Close clearance | Precision structural connections, machine mounting |
| Metric Fine | ISO 965 | 6g | 6H | Medium clearance | Fine-pitch tie rods, vibration-resistant assemblies |
| UNC Coarse | ASME B1.1 | 2A (standard) / 3A (precision) | 2B / 3B | Free fit (2A/2B) / Close (3A/3B) | ASME B31 piping hangers; N. American structural |
| UNF Fine | ASME B1.1 | 2A / 3A | 2B / 3B | Free / Close | Vibration-sensitive; thin-wall connections |
| BSW / BSF | BS 84 | Class 1–2 | Class 1–2 | Standard | Legacy UK plant replacement; maintenance |
2.5 — Pipe Hanger Rod Size Selection Guide
| Pipe Size (NPS) | Nominal Pipe OD (mm) | Typical Hanger Load (kN) | Min Rod Size — Single Rod | Min Rod Size — Double Rod | MSS SP-58 Reference | Notes |
|---|---|---|---|---|---|---|
| ½” – 1″ | 21.3 – 33.4 | 0.5 – 1.5 | M8 / ⅜” | — | Table 4 | Light line; standard M8 rod |
| 1½” – 2″ | 48.3 – 60.3 | 1.5 – 3.0 | M10 / ⅜” | M8 / ⅜” | Table 4 | Process lines; verify thermal load |
| 2½” – 3″ | 73.0 – 88.9 | 2.5 – 5.0 | M10 / ½” | M8 / ⅜” | Table 4 | Standard EPC piping range |
| 4″ | 114.3 | 4.0 – 8.0 | M12 / ½” | M10 / ⅜” | Table 4 | Most common process line |
| 6″ | 168.3 | 7.0 – 14.0 | M16 / ⅝” | M12 / ½” | Table 4 | Heavy insulated line — add insulation weight |
| 8″ | 219.1 | 12.0 – 24.0 | M20 / ¾” | M16 / ⅝” | Table 4 | Verify pipe contents density and insulation |
| 10″ | 273.1 | 18.0 – 36.0 | M24 / 1″ | M20 / ¾” | Table 4 | Spring hanger recommended for hot lines |
| 12″ | 323.9 | 25.0 – 50.0 | M27 / 1″ | M20 / ¾” | Table 4 | Limit rod stress to 0.6 × S_y at temp |
| 16″ | 406.4 | 40.0 – 80.0 | M36 / 1¼” | M24 / 1″ | Table 4 | Double-rod typically required >NPS 14 |
| 20″+ | 508.0+ | 70.0 – 150.0+ | M42+ / 1½” | M30+ / 1¼” | Table 4 + calc. | Engineer-designed spring or constant hanger |
Coatings &
Manufacturing Process
Threaded rod material grade is selected to match the structural load requirement, temperature range, and corrosion environment of the application. RR Hydraulic manufactures and supplies threaded rod in all standard and high-performance grades — from Grade 4.6 carbon steel through A193 B7M NACE, SS 316, and Duplex 2205 — with full EN 10204 3.1 / 3.2 material traceability.
3.1 — Material Grade Overview and Mechanical Properties
| Grade / Class | Spec | UTS (MPa) | Yield (MPa) | Elongation (%) | Temp Range (°C) | Max Hardness (HB) | NACE MR0175 | Primary EPC Application |
|---|---|---|---|---|---|---|---|---|
| Grade 4.6 | ISO 898-1 | 400 | 240 | 22 | −20 to +300 | — | Yes | Light hangers, secondary structural supports |
| Grade 4.8 | ISO 898-1 | 420 | 340 | 14 | −20 to +300 | — | Yes | Standard EPC hanger and support rods |
| Grade 5.6 | ISO 898-1 | 500 | 300 | 20 | −20 to +300 | — | Yes | Medium structural; chemical anchor rods |
| Grade 8.8 | ISO 898-1 | 800 | 640 | 12 | −20 to +300 | 250 HB | Yes (verify HB) | High-load hanger rods; structural tension |
| Grade 10.9 | ISO 898-1 | 1040 | 940 | 9 | −20 to +300 | 295 HB | No | Very high-load tie rods; precision structural |
| ASTM A307 Gr.A | ASTM A307 | 415 | — | — | −29 to +300 | — | Yes | General structural, light hangers (US EPC) |
| ASTM A193 B7 | ASTM A193 | 860–1000 | 725 | 16 | −45 to +454 | 321 HB | No (use B7M) | High-temp equipment base plates; process |
| ASTM A193 B7M | ASTM A193 | 690–862 | 552 | 18 | −45 to +454 | 235 HB max | Yes | Sour service chemical anchors; H₂S zones |
| A2-70 (SS 304) | ISO 3506 | 700 | 450 | 20 | −196 to +300 | Max 250 HV | Yes | Indoor/mild chemical; food/pharma |
| A4-70 (SS 316) | ISO 3506 | 700 | 450 | 20 | −196 to +300 | Max 250 HV | Yes | Marine, offshore, chemical, NACE service |
| A4-80 (SS 316 SH) | ISO 3506 | 800 | 640 | 8 | −196 to +300 | Max 320 HV | Yes | High-load marine / offshore rods |
| Duplex 2205 | UNS S31803 | 620 | 450 | 25 | −50 to +315 | 293 HB max | Yes | Offshore, subsea, sour + chloride |
| A193 B8 (SS 304 stud) | ASTM A193 | 515–690 | 205 | 30 | −196 to +316 | — | Yes | Low-temp, cryogenic process equipment studs |
3.2 — Corrosion Resistance Matrix
| Material | Inland Industrial | Coastal (<1 km) | Marine / Offshore | H₂S / Sour* | Cl⁻ / Seawater | High Temp (>300°C) | Cryogenic |
|---|---|---|---|---|---|---|---|
| Grade 4.8 / 8.8 CS (plain) | Fair (must coat) | Poor | Fail | Conditional* | Poor | Good to 300°C | Not suitable |
| Grade 8.8 CS HDG | Very Good | Good | Fair | Conditional* | Fair | Limited >200°C | Not suitable |
| A193 B7 (plain) | Fair | Poor | Fail | No (use B7M) | Poor | Very Good to 454°C | Fair to −45°C |
| A193 B7M (HDG) | Good | Fair | Fair | Yes (≤235 HB) | Fair | Good to 454°C | Fair to −45°C |
| A4-70 SS 316 | Excellent | Excellent | Very Good | Good | Fair–Good | Good to 300°C | Excellent |
| A4-80 SS 316 SH | Excellent | Excellent | Very Good | Good | Fair–Good | Good to 300°C | Excellent |
| Duplex 2205 | Excellent | Excellent | Excellent | Very Good | Very Good | Limited >315°C | Good to −50°C |
| A193 B8 (SS 304 stud) | Excellent | Good | Fair | Fair | Poor (SCC) | Good to 316°C | Excellent to −196°C |
3.3 — Surface Finish and Coating Options
| Finish | Spec | Thickness (µm) | Salt Spray (h) | Thread Oversize? | Temperature Limit | Application |
|---|---|---|---|---|---|---|
| Plain / Black Mill | ISO 898 as-drawn | — | <24 | No | Per grade | Indoor structural; chemical anchors (best bond) |
| Phosphate + Oil | DIN 50942 | 5–15 | 48–96 | No | Per grade | Short storage; general EPC construction |
| Zinc Electroplate | ASTM B633 / ISO 4042 | 5–25 | 96–300 | Slight — verify nut fit | <200°C | Indoor/outdoor EPC hangers; general structural |
| Yellow Zinc Chromate | ASTM B633 Type III | 5–25 + chromate | 200–500 | Slight | <200°C | Standard outdoor EPC structural rods |
| Hot Dip Galvanise (HDG) | ASTM A153 / ISO 1461 | 45–85 | 2000+ | Yes — oversize nut required | <200°C | Outdoor, coastal, treated timber anchors |
| Geomet / Dacromet | ISO 10683 | 8–12 | 1000–1500 | Minimal | <300°C | Chemical plant; aggressive outdoor service |
| PTFE / Xylan | Proprietary | 15–30 | 1000+ | Minimal | <220°C | Low-friction nut adjustment; anti-galling SS |
| Passivation (SS) | ASTM A967 | Passive layer | 2000+ | No | Per SS grade | All SS rod — standard finish after manufacturing |
3.4 — Manufacturing Process
3.4.1 — Thread Rolling vs Thread Cutting
Threaded rod is manufactured by two methods — thread rolling (cold-forming) and thread cutting (machining). Thread rolling is strongly preferred for structural applications: the cold-forming process displaces material without removal, creating continuous grain flow through the thread form, compressive residual stress at the thread root (improving fatigue life), a work-hardened surface with higher hardness than the parent bar, and a smoother surface finish (Ra ≤ 0.8 µm at thread root) that reduces friction and improves nut assembly torque consistency. Thread cutting produces a weaker, lower-fatigue-life thread that is acceptable only for non-structural, low-load applications.
3.4.2 — Straightness and Dimensional Control
- Straightness: DIN 975 standard: max 1 mm deviation per 1000 mm length (0.1% bow). For chemical anchor rods: straightness must be sufficient to insert at full embedment depth without binding in the drill hole
- Thread OD tolerance: 6g class per ISO 965 — maximum pitch diameter deviation per diameter and pitch combination; verified with thread ring gauges at inspection
- Length tolerance for cut-to-length rods: ±2 mm for rods ≤ 500 mm; ±3 mm for rods 500–2000 mm; ±5 mm for rods > 2000 mm per DIN 975 cut tolerance
- Thread runout at cut ends: Minimum 2 full thread turns free of burrs and chamfered to 45° — ensures clean nut start without cross-threading in field assembly
- HDG oversize check: After galvanising, 5% sample from each lot checked with oversize ring gauge to confirm zinc thickness is within the thread tolerance window for the specified oversize nut
Industry Applications
& Documentation
RR Hydraulic maintains full traceability from raw bar stock to final packed shipment on all threaded rod orders. Dimensional inspection, hardness certificates, coating thickness records, EN 10204 MTRs, NACE compliance statements, and complete EPC export documentation packages are standard on all project-grade supply.
4.1 — Inspection & QC Protocol
4.2 — EN 10204 Material Test Certificate Requirements
| Certificate | Content | Signatory | Standard EPC Requirement | When Mandatory |
|---|---|---|---|---|
| 2.1 | Conformity declaration only | Manufacturer | Non-critical commercial supply | Light general construction utility rods only |
| 2.2 | Non-specific test results | Manufacturer | Standard EPC hanger and support supply | General EPC pipe hanger and structural rod supply |
| 3.1 | Heat/lot traceable mech + chem | Manufacturer’s authorised QC Inspector | Structural anchors, NACE, A193 B7/B7M, SS marine | All chemical anchor rods, NACE sour service, offshore |
| 3.2 | 3.1 + countersigned by TPI | Manufacturer + SGS / BV / DNV / Lloyds | Critical offshore, nuclear secondary, subsea | Offshore structural rods, subsea, nuclear Class 2/3 |
4.3 — Applications by Industry
Pipe Hangers & Support Rods — EPC Process Piping
The highest-volume threaded rod application in EPC projects. M10–M30 Grade 4.8 HDG rod for standard process piping hangers per MSS SP-58 and ASME B31.3. A193 B7 for hot piping systems (steam, high-pressure hydrocarbon) where temperatures exceed 300°C. SS A4-70 rod for offshore topsides and coastal facilities. Hanger rod size per Table 2.D; length field-cut at site. EN 10204 2.2 standard; 3.1 for process-critical hot lines.
Equipment Base Plate Chemical Anchor Assemblies
M16–M36 Grade 8.8 or A193 B7M threaded rod set in epoxy or vinylester resin chemical anchor systems for pump, compressor, and turbine base plate anchoring. NACE sour service: A193 B7M (235 HB max) mandatory. ETA-approved resin system required. EN 10204 3.1 with individual hardness certificate for all NACE anchor rods. Site proof load testing at 1.25 × design load on 5% of installed anchors before base plate grouting and equipment installation.
Offshore Topside Support Structures
SS A4-70 or A4-80 threaded rod for all pipe hanger and support rod assemblies on offshore topsides — carbon steel rods degrade rapidly in continuous marine chloride atmosphere. Duplex 2205 for splash zone and deck-level structural tie rod applications. All rods with EN 10204 3.1 and PMI verification. Matching SS nuts (ASTM F594 or ISO 4032 A4) mandatory — never install carbon steel nuts on SS rod in offshore service.
LNG Plant Cryogenic Hanger Systems
SS A4-70 or A193 B8 (SS 304) threaded rod for cryogenic piping hanger systems in LNG terminal and ethylene plant service at temperatures to −196°C. Impact testing not typically required for austenitic SS (inherently ductile at cryogenic temperatures). Cold-box insulation support rod systems: threaded rod sized for combined pipe weight + insulation weight + thermal contraction load. Constant-effort spring hangers used on main LNG transfer lines to absorb cryogenic contraction movement.
Structural Tie Rod and Bracing Systems
Grade 8.8 or Grade 10.9 threaded rod as tension members in pipe rack bracing frames, modular building diagonal bracing, and equipment platform lateral restraint systems. Turnbuckle assemblies (rod + open-body or closed-body turnbuckle + clevis or fork end fittings) for adjustable-length tension bracing. Pre-tensioned tie rod systems in large-span industrial buildings. Rod buckling check mandatory if any compressive load condition possible.
Power Station Pipe Support Engineering
ASME B31.1 Power Piping hanger rod systems for steam lines, feedwater systems, and boiler drum connections. A193 B7 rod standard for high-temperature (300–454°C) power plant hanger assemblies. Load calculation per MSS SP-58 with allowable rod stress at operating temperature per ASTM A193 B7 elevated-temperature allowable table. Spring hanger selection for thermal movement accommodation — variable spring hangers for moderate movement; constant-effort hangers for large movements >50 mm.
4.4 — Export Packaging Specification
- Threaded rods bundled in standard lengths (1 m, 3 m, 6 m) per diameter, grade, and coating — each bundle tagged with diameter, property class, material grade, coating type, heat/lot number, length, and PO item reference
- VCI (Volatile Corrosion Inhibitor) poly wrap or VCI paper on all plain, phosphated, and zinc-plated carbon steel rods — prevents thread surface oxidation during ocean freight and extended site storage
- Thread end protection: plastic spiral wrap or end cap on both ends of all threaded rod above M20 — protects thread form and prevents thread end burring during bundle handling and transportation
- HDG rods: individual plastic spiral wrap to prevent zinc-to-zinc cold welding between adjacent rods in the bundle during transit; clearly labelled “OVERSIZE NUT REQUIRED — DO NOT ASSEMBLE WITH STANDARD METRIC NUTS”
- SS rods: individually wrapped and segregated from carbon steel hardware in the same shipment — prevents galvanic contact and SS surface contamination; SS grade clearly labelled (A4-70 / A4-80 / Duplex) on each bundle tag
- Cut-to-length rods: individual identification tag on each rod for chemical anchor applications — heat number, grade, diameter, length, and coating — enabling individual rod traceability in the anchor installation log
- ISPM-15 heat-treated timber crates for all international export; heavy rods (M36 and above in 6 m lengths) in individual crates secured against axial movement during shipping
- Documentation: packing list, EN 10204 MTC, hardness certificate (NACE lots), coating certificate, and FAI report enclosed with each shipment — cross-referenced to each bundle lot tag
4.5 — Complete EPC Project Documentation Package
| # | Document | Standard / Format | Mandatory / Conditional | Notes |
|---|---|---|---|---|
| 01 | Material Test Certificate (MTC) | EN 10204 2.2 / 3.1 / 3.2 | Mandatory — grade per project spec | Bar / wire lot heat-traceable |
| 02 | Chemical Composition Report | Ladle analysis — bar stock lot | Mandatory — 3.1 / 3.2 orders | Per ISO 898-1 / ASTM A193 chemistry limits |
| 03 | Mechanical Properties Report | UTS, yield, elongation, hardness | Mandatory — 3.1 / 3.2 orders | Full-section or threaded specimen tensile test |
| 04 | Hardness Test Report | ASTM E10 Brinell / ISO 6506 | Mandatory — NACE sour service | A193 B7M: individual rod ≤235 HB reported |
| 05 | Dimensional Inspection Report | Per DIN 975 / ISO 965 / ASME B1.1 | Mandatory | Thread gauging, OD, straightness, length |
| 06 | Thread Gauge Report | ISO 965 Class 6g (Go/No-Go) | Mandatory | 100% gauging on each lot; calibrated gauges |
| 07 | Surface Finish / Coating Certificate | ISO 4042 / ASTM A153 / ISO 10683 | Mandatory — all coated supply | Coating thickness + salt spray per lot |
| 08 | HDG Oversize Thread Check Report | Oversize ring gauge per DIN 267-10 | Mandatory — all HDG rod supply | Confirms correct zinc build-up; nut compatibility |
| 09 | PMI Report (XRF) | Per lot — SS / duplex / ASTM A193 | Mandatory — SS, duplex, NACE lots | A4-70 vs A4-80; B7M vs B7 differentiation |
| 10 | Tensile / Proof Load Test Report | ISO 898-1 / ASTM F606 / ASTM A193 | Mandatory — Grade 8.8+; A193 B7/B7M | Full-section tensile; UTS + yield per spec |
| 11 | NACE Compliance Statement | Hardness + grade declaration | Mandatory — sour service supply | References rod heat number + hardness result |
| 12 | First Article Inspection (FAI) Report | Project-specific format | Mandatory — new configurations / first lots | Released before batch supply proceeds |
| 13 | TPI Witness Certificate | SGS / BV / DNV / Lloyds | Conditional — EN 10204 3.2 / offshore | Co-witness at manufacturer works |
| 14 | ETA Document Reference | Product ETA document number | Conditional — chemical anchor rod supply | Confirms rod grade per ETA resin approval |
| 15 | ISO 9001:2015 Certificate | Third-party QMS certification | Mandatory — all EPC projects | Scope covers threaded rod manufacture |
| 16 | Country of Origin Certificate | Chamber of Commerce | Mandatory — all export | HS tariff code for customs classification |
| 17 | Packing List | Item-level per shipment | Mandatory | Cross-references lot numbers and MTC |
| 18 | Commercial Invoice | Per INCOTERMS 2020 | Mandatory | Includes HS tariff code |
| 19 | Bill of Lading / Air Waybill | Per freight mode | Mandatory | Issued by freight forwarder |
4.6 — ISO and Quality System Compliance
ISO 9001:2015
Quality Management System covering bar stock supplier qualification, thread rolling process control, dimensional inspection, heat treatment verification (Grade 8.8+), chemical composition control, coating process QC, hardness testing protocol, and full lot traceability from bar stock to finished rod. Mandatory for EPC, structural, and O&G project procurement qualification. RR Hydraulic holds current ISO 9001:2015 certification with scope covering threaded rod manufacture.
EN 1992-4 (Eurocode 2 Part 4)
Design of fastenings for use in concrete. Governs threaded rod design when used as the steel element in chemical anchor systems — pull-out, concrete cone, splitting, and shear failure modes all require verification per EN 1992-4. The structural design basis for all EPC chemical anchor rod sizing in European and international projects. Safety factors γ_M2 = 1.5–2.5 per failure mode. Always used with ETA product-specific bond strength data.
MSS SP-58
Pipe Hangers and Supports — materials, design, manufacture, and selection. The primary pipe support engineering standard for threaded rod sizing in EPC process piping projects. Defines allowable rod stress as 0.6 × S_y at design temperature; provides rod size selection tables for standard pipe sizes and loads. Used with ASME B31.1 / B31.3 pipe support design requirements on EPC projects.
ISO 10474
Steel and steel products — inspection documents. Source framework for EN 10204 certificate types. Some EPC project and structural engineering specifications reference ISO 10474 Type 3.1.B for threaded rod supply — this maps to EN 10204 3.1. RR Hydraulic provides documentation in either format and cross-maps certificate types in the supply documentation for legacy specification compliance on request.
Submit your rod schedule, diameter, grade, length, material, coating, and quantity to RR Hydraulic for a complete, certified commercial offer.